Since the war between Sparta's army and Athens' navy would have lasted a long time, Sparta relied on a more traditional strategy of Greek warfare. They thought that if they invaded Attica and destroyed all the crops there, they thought that it would force Athens to plead for peace or come out and fight.
They thought that by a land attack Sparta could easily take Athens' army because Athens' army was, compared to Sparta's, small, weak, and not as disciplined. While Athens' navy compared to Sparta's, was exceedingly more superior.
But, there was one defect in this plan; Athens', unlike other Greek cities, food supply came principally from Egypt and Crimea. This means that Athens could not be starved into surrender nor be made to fight a set up battle by occational occupation of individual citizen's farm land.
The old king of Sparta, Archidamus, knew about this and tried to worn his people about it, but the Spartans were sure and confident in a quick victory so they continued with the annihilation plan.
Pericles had his own strategy. He knew that Athens' city walls were impregnable and could not be overthrown and were also connected to the sea so the navy would be able to keep the food supply going. So he went for the defence strategy of attrition.
When Sparta invaded Attica, most of rural population moved into cites. Athens itself became a impenetrable island to attack.
Its great fleet would secure the empire against revolts from within and attacks from without and take the offensive to raid the Peloponnesian coast.
Meanwhile, every spring and autumn the Athenian land army would devastate the lands of Sparta's allies (especially Megara) at the Corinthian Ismuth, while the Spartans were home tending to their own crops. If Megara could be recovered, then Spartan land access to Attica would be blocked and her Theban allies would not dare come down from the north unaided.
Pericles' strategy had its weakness too.
He was too fearful of the effect that high casualties would have on public sentiment in a democracy, if he had conducted more aggressive offensive military actions. He had not seen the opportunities for combined land and naval actions to bring a higher intensity of war to Spartan territory with little risk in order to hasten the effect of the attrition on Sparta. The defect essentially was that the Athenian people's morale proved unequal to the strain, and, after his death, rushed into rash attempts to over-reach their means.
Meanwhile, the Spartans were stoic and persistent in the face of failure, until they found foreign resources sufficient to turn the tables on Athens.
Plague struck Athens and though it seems they would have spread it, no other city-state suffered near as much. Athens' own leader Pericles died from it. All of Athens' attacks were weak and of no bother to Sparta.
In Athens, the economy was rapidly falling. This led to Pericles ditching strategic opportunities he could use with his navy.
In 430, Athens offered peace and Sparta refused. Then, in late 429, Athens won two important naval battles (Chalcis and Naupactus) and Sparta started to regret their refusal. A year later Spartans ally, Mitylene was being attacked and Sparta just left them to surrender. This was counterdicted by Plataea, Athens' ally, surrendred because Thebes had conmpletely destroyed their city and population. But, this did not stop Athens. They began to take the lead, yet only after a big loss. It seems the war was at a stalemate.
The First Phase: Phase 1
(431-427)